Obesity develops due to positive energy balance, when energy intake exceeds energy expenditure. One factor that may influence energy intake is individual differences in the rate of habituation to food. The rates of salivary habituation or habituation of behavioral responding for food predict energy intake, with slower habituation related to greater energy intake. We have shown overweight or obese youth and adults habituate slower to repeated food cues than leaner youth and adults, but it is not known whether this is a result of being overweight, or whether slower habituation is a risk factor for zBMI gain. This can only be tested using prospective designs in which children who differ in their rate of habituation are studied prospectively to evaluate risk factors for zBMI increases. The goal of this application is to study individual differences in habituation of behavioral responding for food and salivary habituation as risk factors for zBMI and body fat changes over a three year period in 200 8 to 10 year-old non-overweight children. Mixed effects regression models will be used to study whether aggregate measures of baseline salivary habituation and/or habituation of behavioral responding for food (Specific Aim 1) or habituation to foods that differ on basic taste characteristics (sweet, savory, salty, Specific Aim 1a) are independent predictors of trajectories of zBMI and body fat, to assess the relationship between habituation of behavioral responding for food or salivary habituation and energy intake (Specific Aim 2), to assess developmental trajectories in habituation over time (Specific Aim 3), to test the relationship between reflexive, physiological (salivation) and behavioral (responding for food) measures of habituation (Specific Aim 4), and assess whether relative reinforcing value of food and eating in the absence of hunger are risk factors for child zBMI gain (Specific Aim 5). PUBLIC HEALTH RELEVANCE: Cross sectional data have shown slower habituation is related to greater energy intake, and habituation is slower for overweight/obese compared to leaner youth, but it is not known whether this is a result of being overweight, or whether slower habituation is a risk factor for weight gain. The goal of this application is to study individual differences in reflexive, physiological (salivation) and behavioral (responding for food) habituation as risk factors for alterations in zBMI and body fat over a three year period in 200, 8 to 10 year-old non-overweight children. This application will provide the first test of the hypothesis that slow habituation to food is a risk factor for increases in zBMI in non-overweight youth.